1. Field of the Invention
The present invention relates to a stator for a starter motor used in vehicles and the like, and more particularly, to a stator for a starter motor having a bendable stacked core.
2. Description of the Related Art
FIG. 14 is a perspective view showing the structure of a stator for a conventional starter motor; FIG. 15 is a plan view of the stator; and FIG. 16 is a perspective view showing an assembly process of the stator.
In the figures, four poles 104 are disposed in a cylindrical yoke 103. Field coils 107 are mounted on the four poles 104.
In the conventional stator arranged as described above, the yoke 103 is arranged as the cylindrical yoke (xe2x80x9cbent yoke portionxe2x80x9d) by rounding a sheet member and welding the joints thereof. Spigot portions 106, which are formed at the ends of the yoke 103 in the axial direction thereof, are processed by machining, and fitted to not shown brackets.
Further, the poles 104 are made in a different process by, for example, forging or the like and mounted on the yoke 103 later. Furthermore, the field coils 107 are previously wounded in a different process and the spaces between wires are previously subjected to insulation processing by powder coating or the like.
The conventional stator arranged as described above is assembled in such a manner that, first, the electric field coils 107, which have been wounded and subjected to the insulation processing, are mounted on the poles 104. Then, the poles 104 are mounted on the yoke 103 through the mounting holes 103a thereof by caulking, screws or the like.
In the stator for the starter motor arranged as described above, the yoke 103 must have a predetermined thickness because a yoke made of a thin sheet member cannot achieve its function. Thus, the yoke 103 is made in such a manner that a thick sheet member is cut off by a large press and gradually rounded so as to be formed in a cylindrical shape, then the cylindrical thick sheet member is subjected to a drawing process to provide it with accuracy by making the deformed portions of the cylindrical member to a perfect cylindrical shape. Thereafter, the spigot portions 106 are machined at the ends of the cylindrical member in the axial direction thereof and the mounting holes 103a are drilled to the cylindrical member.
The conventional so-called xe2x80x9cbent yoke portionxe2x80x9d made by the above method requires many dedicated apparatuses such as a large press, welder, outside diameter drawing machine, lathe, drilling machine, coating machine, and the like. Further, many processes are necessary to manufacture the xe2x80x9cbent yokexe2x80x9d and the respective processing apparatuses are large in size, from which a problem arises in the manufacture of the xe2x80x9cbent yokexe2x80x9d.
An object of the present invention, which was made to solve the above problems, is to provide a stator for a starter motor whose manufacturing cost can be reduced.
In the stator, which is composed of a stacked core, for the starter motor according to the present invention, the stacked core being arranged such that a plurality of sheet members each having a yoke portion and a pole portion are disposed like a band, adjacent sheet members are stacked and coupled with each other so that the ends of the yoke portions thereof are overlapped, the plurality of sheet members are made to an annular shape by being bent at the coupled portions thereof to cause the pole portions to face the center of the annular shape, and the plurality of sheet members are formed in at least an approximately linear shape when developed, resin winding cores are interposed between the pole potions and wires wound around the pole portions.